ASME SA542 Steel Plate
ASME SA542 Type A Class 4a | SA542-A Cl.4a Vessel Steel Plate
ASME SA542 Type A Class 4a, also written SA542 Type A Class 4a, SA542-A Cl.4a, and companion ASTM A542 Type A Class 4a. This designation is quenched-and-tempered chromium-molybdenum pressure-vessel plate under ASME SA-542/SA-542M. Type A sets the heat-analysis chemistry (2¼Cr-1Mo). Class 4a sets the tensile line: yield strength min 60 ksi [415 MPa], tensile strength 85–110 ksi [585–760 MPa], elongation min 18% in 2 in. [50 mm]. A542/SA542 uses Type and Class only (no Grade number). Confirm the ASTM or ASME edition named on the purchase order before mill release. gangsteel produce and export this Type and Class cut to size; EN 10204 3.1 or 3.2 mill certificates and impact/PWHT/NDE supplements are supplied when written on the order.
ASME SA542 Type A Class 4a Chemical Composition
Heat-analysis limits for Type A. Product-analysis tolerances and footnotes follow the contracted edition of ASME SA-542/SA-542M. Values below are heat analysis, %.
| Element (heat analysis) | Type A, % |
|---|---|
| Carbon (C) | 0.15 max |
| Manganese (Mn) | 0.30–0.60 |
| Phosphorus (P), max | 0.025 |
| Sulfur (S), max | 0.025 |
| Silicon (Si), max | 0.50 |
| Chromium (Cr) | 2.00–2.50 |
| Molybdenum (Mo) | 0.90–1.10 |
| Copper (Cu), max | 0.40 |
| Nickel (Ni), max | 0.40 |
| Vanadium (V), max | 0.03 |
Type A and Type B are the two 2¼Cr-1Mo chemistries in A542/A542M. Order the Type required by the vessel specification; do not substitute Type B without engineering approval.
ASME SA542 Type A Class 4a Mechanical Properties
| Property | Class 4a |
|---|---|
| Tensile strength | 85–110 ksi [585–760 MPa] |
| Yield strength, min | 60 ksi [415 MPa] |
| Elongation in 2 in. [50 mm], min, % | 18 |
Class tensile values are Class-based, not Type-specific, within the combinations permitted by ASME SA-542/SA-542M. Apply ASTM A20/A20M elongation adjustment where thickness requires. Classes 4 and 4a require transverse Charpy V-notch testing: 40 ft·lbf [54 J] average of three specimens and 35 ft·lbf [48 J] for one specimen. Class 4a impact test temperature is 0°F [−18°C]. Charpy impact (where not already Class-required), PWHT simulation, and NDE follow the purchase order and applicable ASME Section requirements when specified.
Application Areas
ASME SA542 Type A Class 4a is selected for welded pressure equipment that needs quenched-and-tempered 2¼Cr-1Mo plate at the Class 4a strength line. Typical engineered uses include:
- Heavy-wall pressure vessels and reactors in refining and petrochemical service where the design specifies A542/SA542 Type A Class 4a (or dual-marked companion designation when Code-ordered).
- Hydroprocessing and hydrotreating equipment shells, heads, and thick-section components that require this Cr-Mo or Cr-Mo-V alloy content with quenched-and-tempered mechanical properties rather than a normalized-and-tempered Cr-Mo specification alone.
- High-integrity boilers and pressure vessels where the purchaser’s material specification names Type A chemistry and Class 4a tensile limits.
- Repair, replacement, and project plate cut to size for fabricators working to ASME Section VIII or project vessel specifications that call out A542/SA542 Type A Class 4a.
Final fitness for a given design temperature, hydrogen service, PWHT cycle, or sour-service supplement is project-specific. Order the exact Type, Class, edition, and test package required by the vessel drawing and Code.
Delivery Condition
Under ASME SA-542/SA-542M, Type A Class 4a plate is normally furnished in the quenched-and-tempered (QT) condition so that Class 4a tensile and yield requirements are met at delivery. As-rolled or normalized-only shipment does not meet this Class unless the purchaser performs the full quench-and-temper cycle under the specification (see Heat Treatment Process).
| Item | Requirement | Order confirmation |
|---|---|---|
| Standard final condition | Quenched and tempered (QT) to Class 4a mechanical properties | State QT delivery on the PO unless another route is agreed in writing |
| Purchaser heat-treatment exception | Purchaser may perform final QT when permitted by ASME SA-542/SA-542M; manufacturer pre-shipment temper still applies (see Heat Treatment Process) | Name who performs final QT and required mill temper before shipment |
| Marking | ASME SA-542 (or ASTM A542 when product-ordered) with Type A and Class 4a; dual marking by agreement when editions align | Confirm ASTM, ASME, or dual marking on the order |
| Certification | Mill test documentation for heat/product analysis and mechanical results as ordered | EN 10204 3.1 or 3.2, and any third-party witness, subject to enquiry and order confirmation |
| Supplementary tests | Impact, PWHT simulation, NDE, and other project extras when specified | List each supplement, acceptance, and temperature on the PO |
Certificate form, analysis reporting, and supplements are not assumed as open guarantees: confirm them with the enquiry and order. Delivery marking must show Type A Class 4a as ordered.
Heat Treatment Process
Plate heat treatment for ASME SA542 Type A Class 4a is distinct from vessel post-weld heat treatment (PWHT). The plate route is austenitize, quench, and temper to Class 4a. Fabrication PWHT follows the applicable ASME Section and the fabricator’s WPS and must be ordered separately when simulated or recorded on plate tests.
| Step | Requirement | Order confirmation |
|---|---|---|
| Austenitize | Heating for quench as required to develop Class 4a properties after temper | No fixed temperature, hold time, or rate is stated here; confirm mill practice against the contracted edition if required on the PO |
| Quench | Cooling from austenitizing to produce the as-quenched structure for temper | Quench medium and parameters follow mill practice within the specification; name any purchaser limit on the order |
| Temper (final QT by manufacturer) | Minimum tempering temperature for Type A Class 4a: 1250°F [675°C] | Confirm Class 4a temper requirement and any higher project minimum on the PO |
| Manufacturer temper when purchaser performs final QT | If the purchaser performs the quench-and-temper cycle, the manufacturer shall temper before shipment at not lower than 1050°F [565°C] for Types A, B, C, and D | State purchaser final QT and required pre-shipment temper on the order |
| Vessel PWHT (not plate delivery temper) | Separate from plate QT; governed by Code, drawing, and WPS | Order PWHT simulation or recorded cycles only when written on the PO |
Only the minimum temper of 1250°F [675°C] for Type A Class 4a is given from the verified specification data used for this page. Austenitizing temperature (unless a Type minimum is listed above), quench medium, hold times, and heating/cooling rates are not fixed on this page and remain subject to mill practice and order confirmation. Impact test temperature and acceptance, when required, must be named on the order.
Size and Supply Range
ASME SA-542/SA-542M states a minimum thickness of 3/16 in. [5 mm]. Maximum thickness is limited by the ability of the plate to meet the specified mechanical properties after quench and temper. Width and length are cut to the dimensions stated on the purchase order, within mill and processing capability for the order. Available thickness, width, length, lead time, certificate type (EN 10204 3.1 or 3.2), and any cutting or test extras are subject to enquiry and order confirmation. State thickness × width × length, Type A Class 4a, edition, and required supplements on the RFQ.
Comparison with ASTM A533
Both ASME SA542 Type A Class 4a and ASTM A533 Grade A Class 1 (also written A533 Type A Class 1) are quenched-and-tempered alloy steel plates for welded pressure vessels, but they are not interchangeable.
| Item | ASME SA542 Type A Class 4a | ASTM A533 Grade A Class 1 |
|---|---|---|
| Alloy family | Cr-Mo (Type A: 2¼Cr-1Mo) | Mn-Mo (Type/Grade A: no specified nickel) |
| Naming | Type + Class (no Grade number) | Type/Grade + Class (commercial orders often say Grade A) |
| Heat treatment | Quenched and tempered | Quenched and tempered |
| This page Class 4a yield, min | 60 ksi [415 MPa] | 50 ksi [345 MPa] (A533 Class 1) |
| This page Class 4a tensile | 85–110 ksi [585–760 MPa] | 80–100 ksi [550–690 MPa] (A533 Class 1) |
| Elongation in 50 mm, min | 18% | 18% (A533 Class 1) |
See the ASTM A533 Steel Plate hub for other A533 grades and classes. A533 Class numbers do not map one-to-one onto A542 Class numbers. Do not substitute A533 Grade A Class 1 for ASME SA542 Type A Class 4a (or the reverse) without a design and purchasing change.
Equivalent / Related Materials
The table lists companion designations and chemistry-family related materials. Rows marked “similar / related” are engineering cross-references only—not proven drop-in equivalents and not automatic Code interchangeability. Dual certification requires the stricter combined limits on the purchase order and MTC.
| Standard / region | Designation | Relationship | Reference |
|---|---|---|---|
| American (ASTM companion) | ASTM A542 Type A Class 4a | Companion designation when editions align; dual marking by agreement | Order ASTM A542 Type A Class 4a when the vessel specification requires the ASTM name |
| American (related Cr-Mo) | ASTM A387 / ASME SA387 Grade 22 Class 1 / Class 2 | Similar 2¼Cr-1Mo chemistry family; typically normalized-and-tempered elevated-temperature material—not an A542 QT Class substitute | A387 Grade 22 Class 1 · A387 Grade 22 Class 2 · A387 hub |
| American (related QT) | ASTM A533 Grade A Class 1 | Also quenched-and-tempered vessel plate; Mn-Mo chemistry—related product family only | A533 Grade A Class 1 · A533 hub |
| Chinese GB (similar / related) | GB/T 713 12Cr2Mo1R | 2¼Cr-1Mo pressure-vessel grade family; not a proven one-to-one QT Class interchange with this A542 Type/Class | GB/T 713 12Cr2Mo1R · GB/T 713 hub |
| Chinese GB (V-bearing related) | GB/T 713 12Cr2Mo1VR | Related Cr-Mo-V vessel grade; different chemistry and route from A542 Type A | GB/T 713 12Cr2Mo1VR |
| Japanese JIS | No confirmed direct equivalent | Related Cr-Mo plate designation SCMV4 (JIS G4109) is a chemistry-family reference only and is not interchangeable with ASME SA542 Type A Class 4a | — |
No automatic one-to-one equivalent across EN/JIS/GB is claimed for ASME SA542 Type A Class 4a. Order and certify the designation required by the vessel specification.
FAQ
1. What is ASME SA542 Type A Class 4a?
It is quenched-and-tempered pressure-vessel plate under ASME SA-542/SA-542M. Type A fixes the 2¼Cr-1Mo heat-analysis chemistry. Class 4a fixes strength: yield min 60 ksi [415 MPa], tensile 85–110 ksi [585–760 MPa], elongation 18% min in 50 mm. Plates are supplied to order with mill certificates when this Type and Class are named on the purchase order.
2. How does ASME SA542 Type A Class 4a relate to ASTM A542 Type A Class 4a?
For the same Type and Class, ASTM A542 and ASME SA-542 are companion designations used for product versus Code ordering. Chemistry and Class tensile limits are intended to align when the contracted editions match. Order the name required by the vessel specification; dual marking is by agreement.
3. What mechanical values apply to Class 4a?
Class 4a tensile strength is 85–110 ksi [585–760 MPa]; yield min 60 ksi [415 MPa]; elongation in 50 mm min 18%. These Class values apply to Types ordered to Class 4a under the permitted combinations in ASME SA-542/SA-542M. Thickness-dependent elongation adjustment follows A20/A20M when required.
4. What distinguishes Type A / which Type–Class combinations are allowed?
Type A is one of the two 2¼Cr-1Mo chemistries in A542/A542M (with Type B). Other Types use different Cr-Mo or Cr-Mo-V chemistries. Not every Type may be ordered to every Class; specify a permitted Type and Class combination from ASTM A542/A542M as named on the drawing and purchase order.
5. Is ASME SA542 Type A Class 4a interchangeable with A387 Grade 22 or A533 Grade A Class 1?
No automatic swap. A387 Grade 22 is a different Cr-Mo pressure-vessel heat-treatment specification. A533 Grade A Class 1 is a Mn-Mo quenched-and-tempered specification. ASME SA542 Type A Class 4a must be ordered and certified as A542/SA542 Type A Class 4a.
6. What thickness and certificate options should be confirmed on the order?
Specification minimum thickness is 3/16 in. [5 mm]; maximum thickness depends on meeting Class 4a after quench and temper. Confirm thickness × width × length, edition, impact/PWHT/NDE, and EN 10204 3.1 or 3.2 by enquiry and order confirmation.
Related Links
- ASME SA542 Type A Class 4a
- Pressure Vessel Steel Plate
- ASTM A533 Steel Plate
- ASTM A533 Grade A Class 1
- ASTM A387 Steel Plate
- ASTM A537 Steel Plate
- GB/T 713 Steel Plate
RFQ: thickness × width × length, Type A Class 4a, ASME SA-542/SA-542M edition, impact/PWHT/NDE, 3.1 or 3.2 — admin@gangsteel.com / jack@gangsteel.com.